"Piranha Brothers" is a Monty Pythonsketch, first seen in Series 2, Episode 1 (Face the Press) of Monty Python's Flying Circus, originally transmitted on September 15, 1970. The premise is a BBC current affairs documentary, inexplicably entitled Ethel the Frog, covering the exploits of the fictional brothers Doug and Dinsdale Piranha, who employed a combination of "violence and sarcasm" to intimidate the London underworld and bring the city to its knees. Dinsdale was said to be afraid of "Spiny Norman", an apparently imaginary gigantic hedgehog whose reported size varied on Dinsdale's mood.

The sketch constitutes a pastiche of the real life story of the Kray twins, famous gangsters in the East End of London in the 1950s and 1960s. Doug and Dinsdale Piranha were loosely based on Reggie and Ronnie Kray, and the policeman who pursued them, Harry "Snapper" Organs, was loosely based on the policeman who led the investigation against the Krays, Detective Superintendent Leonard "Nipper" Read. The Piranhas' methods seem to resemble more closely those used by the rival the Richardson Gang and their associate "Mad" Frankie Fraser. Spiny Norman is possibly a subtle reference to the notorious former head of the London Drug Squad, Detective Sergeant Norman Pilcher.

A slightly re-worked version of the sketch also appeared on the album Another Monty Python Record, which opened by announcing that the brothers had recently been sentenced to 400 years imprisonment for crimes of violence. In addition to Doug's wide repertoire of sarcasm, hyperbole is also included. Rather than nuke Luton Airport, the brothers are said to have napalmedCheltenham. This version ends with one of the Piranha Brothers associates interrupting the recording and "accidentally" scratching the record, causing a continuous loop in the album's run out groove. An almost word-for-word transcript appeared in Monty Python's Big Red Book.